1. Field of the Invention
The present invention relates to a plasma display panel having slanted discharge electrodes disposed so as to generate discharge in diagonal corners of discharge cells.
2. Description of the Related Technology
In general, plasma display panels (PDPs) are flat panel display devices in which a discharge gas is injected between two substrates so as to generate a discharge. Phosphor layers are excited by ultraviolet radiation generated due to the discharge to display desired numbers, characters, and images.
A conventional three-electrode surface discharge PDP includes a front substrate, a plurality of pairs of sustain electrodes disposed on an inner surface of the front substrate, and a front dielectric layer covering the sustain electrode pairs. The PDP also includes a protective layer coated on the front dielectric layer, a rear substrate facing the front substrate, address electrodes formed on the rear substrate, and a rear dielectric layer covering the address electrodes. The PDP further includes barrier ribs installed between the front substrate and the rear substrate, and red, green, and blue phosphor layers formed on inner surfaces of the barrier ribs.
Each sustain electrode pair generally includes an X electrode and a Y electrode disposed in parallel to the X electrode. The X electrode includes a first transparent electrode line, and a first bus electrode line electrically connected to the first transparent electrode line. The Y electrode includes a second transparent electrode line, and a second bus electrode line electrically connected to the second transparent electrode line. Each Y electrode generally crosses the address electrodes.
In a conventional PDP having the above structure, electrical signals are applied to the Y electrode and the address electrode to select a discharge cell. The electrical signals are alternately applied to the X and Y electrodes and generate a surface discharge along the surface of the front substrate, thereby generating ultraviolet radiation. Then, the red, green, and blue phosphor layers coated in the selected discharge cells emit visible light and display a still image or a moving picture image.
Japanese Laid-open Patent No. 2002-216636 discloses an electrode structure for improving an aperture rate. Japanese Laid-open Patent No. 1999-265661 discloses an electrode structure with an improved aperture rate by reducing the number of sustain discharge electrodes located on the front substrate. Japanese Laid-open Patent No. 1996-138558 discloses an electrode structure with a high level of brightness achieved by increasing an aspect ratio.
However, conventional PDPs such as those described in the above Japanese publications cause the following problems.
The first and second bus electrodes, which are formed of conductive metal, are electrically connected to each other so as to improve the conductivity of the first and second transparent electrode lines. The first and second transparent electrode lines are formed of a transparent conductive material such as indium tin oxide (ITO) so as to reduce line resistance.
Although the first and second bus electrodes have good conductivity, since they are formed of opaque metal, they reduce the aspect ratio of the front substrate. Accordingly, the brightness of the plasma display panel is reduced and the discharge efficiency is lowered.
In addition, i) the sustain discharge electrode pair and ii) the front dielectric layer and iii) the protective layer are sequentially formed on the inner surface of the front substrate so that they block the light transmitting path of the PDP. Thus, the light transmittance is less than 60%. Therefore, the performance of the PDP decreases.
Furthermore, when the PDP is driven for a long time, the discharge is diffused toward the phosphor layer. Due to the electric field, charged particles of the discharge gas cause ion-sputtering of the phosphor layer, resulting in a permanent residual image.
The discharge starts from a discharge gap between the X and Y electrodes and diffuses to edges of the X and Y electrodes, along the plane of the front substrate. Thus, the discharge space is limited.
When a high concentration of Xe gas is used to fill the discharge cell, typically 10% by volume or more, ionization and excitation of the electrons cause the generation of excitons, and thus, the PDP brightness and discharge efficiency may increase. However, if high concentration Xe gas is used, a higher initial discharge firing voltage is required.